The term streaming media describes the playback of media on a playback device, where the media is stored on a server and continuously sent to the playback device over a network during playback. Typically, the playback device stores a sufficient quantity of media in a buffer at any given time during playback to prevent disruption of playback due to the playback device completing playback of all the buffered media prior to receipt of the next portion of media. Adaptive bit rate streaming or adaptive streaming involves detecting the present streaming conditions (e.g. the user's network bandwidth and CPU capacity) in real time and adjusting the quality of the streamed media accordingly. Typically, the source media is encoded at multiple bit rates and the playback device or client switches between streaming the different encodings depending on available resources.
Adaptive streaming solutions typically utilize either Hypertext Transfer Protocol (HTTP), published by the Internet Engineering Task Force and the World Wide Web Consortium as RFC 2616, or Real Time Streaming Protocol (RTSP), published by the Internet Engineering Task Force as RFC 2326, to stream media between a server and a playback device. HTTP is a stateless protocol that enables a playback device to request a byte range within a file. HTTP is described as stateless, because the server is not required to record information concerning the state of the playback device requesting information or the byte ranges requested by the playback device in order to respond to requests received from the playback device. RTSP is a network control protocol used to control streaming media servers. Playback devices issue control commands, such as “play” and “pause”, to the server streaming the media to control the playback of media files. When RTSP is utilized, the media server records the state of each client device and determines the media to stream based upon the instructions received from the client devices and the client's state.
In adaptive streaming systems, the source media is typically stored on a media server as a top level index file pointing to a number of alternate streams that contain the actual video and audio data. Each stream is typically stored in one or more container files. Different adaptive streaming solutions typically utilize different index and media containers. The Synchronized Multimedia Integration Language (SMIL) developed by the World Wide Web Consortium is utilized to create indexes in several adaptive streaming solutions including IIS Smooth Streaming developed by Microsoft Corporation of Redmond, Wash., and Flash Dynamic Streaming developed by Adobe Systems Incorporated of San Jose, Calif. HTTP Adaptive Bitrate Streaming developed by Apple Computer Incorporated of Cupertino, Calif. implements index files using an extended M3U playlist file (.M3U8), which is a text file containing a list of URIs that typically identify a media container file. The most commonly used media container formats are the MP4 container format specified in MPEG-4 Part 14 (i.e. ISO/IEC 14496-14) and the MPEG transport stream (TS) container specified in MPEG-2 Part 1 (i.e. ISO/IEC Standard 13818-1). The MP4 container format is utilized in IIS Smooth Streaming and Flash Dynamic Streaming. The TS container is used in HTTP Adaptive Bitrate Streaming.
To provide a consistent means for the delivery of media content over the Internet, the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) have put forth the Dynamic Adaptive Streaming over HTTP (DASH) standard. The DASH standard specifies formats for the media content and the description of the content for delivery of MPEG content using HTTP. In accordance with DASH, each component of media content for a presentation is stored in one or more streams. Each of the streams is divided into segments. A Media Presentation Description (MPD) is a data structure that includes information about the segments in each of the stream and other information needed to present the media content during playback. A playback device uses the MPD to obtain the components of the media content using adaptive bit rate streaming for playback.
Live streaming refers to the streaming of media that is simultaneously recorded and broadcast in real time to an audience, and may employ adaptive streaming technologies. Live streaming is often used to broadcast sporting events, news, social media events, interviews, competitions and a variety of other types of events. During the streaming of a live event, it is common for broadcasters to include commercials during selected breaks in the broadcasting of the event. These breaks may occur, for example, during a timeout of a ball game, a judging period for certain sporting events, a preparation or setup period for journalists or hosts, and/or various other types of breaks during which broadcast of the live event is undesired or not required.